It is conventional practice to display meat, poultry, and other food products in individual packages which comprise a supporting tray with an absorbent pad placed between the upper surface of the tray and the food product, to absorb any juices or liquids, such as blood, exuded from the food product. To prevent or retard any migration of the liquids from the absorbent pad back to the food product, the absorbent pads are typically enveloped in a moisture impermeable film that has a number of perforations on the surface facing the tray.
The use of an absorbing pad suffers from the big disadvantage of the labor cost involved in inserting it into a tray, including the costs of a padding machine specifically designed for this purpose. Another disadvantage of this system is the aesthetics of the pad when filled with liquids, particularly blood. Still another disadvantage can be experienced when the pad is saturated with the liquids, as it then tends to stick to the food product and must be physically separated therefrom by the consumer after the package is opened.
One approach to solve the above problems has been to provide a packaging tray having integral means for removing the fluids exuded from the food products, without requiring the use of a separate pad.
Several patents and patent applications have thus been published describing receptacles for packaging food products exuding fluids made with a laminate wherein an absorbing layer is positioned on top of a support layer or between a support layer and a food-contact perforated layer. Examples of these receptacles are described in GB-A-2,322,100, WO-A-99/32286, EP-A-878,481, EP-A-965,426, EP-A-642,907, and WO-A-98/12126.
None of these documents however makes reference to the possibility of obtaining a self-absorbing tray (i.e. a tray with integral means capable of absorbing the fluids) having gas-barrier properties.
On the other hand gas-barrier properties for a packaging material have become extremely important. By using gas-barrier packaging material, it is in fact possible to package the food product under a modified atmosphere especially designed to increase the shelf life of the packaged product. It is thus possible for instance to prepare suitable food packages, e.g. meat packages, at a central unit and then distributing them to supermarkets and small shops.
EP-B-520,509 relates to a thermoformed self-absorbing packaging element with gas-barrier properties. What is described in EP-A-520,509 is a container comprising an absorbing layer positioned between a substrate layer and an inner, food-contact porous drainage layer wherein gas barrier properties are provided by an outermost layer of a gas-barrier material.
Following the teaching of EP-A-520,509 it is however not always possible to obtain the claimed gas-barrier properties. On the contrary, in most of the cases and independently on the gas-barrier properties of the outer gas-barrier layer and of the gas-barrier film that closes the mouth of the tray, the atmosphere within a package obtained by following the teaching of EP-A-520,509 does equilibrate with the outer atmosphere in a very short time. In fact when a foamed or a fibrous layer is employed in the construction of the tray, gases can permeate through the lateral edges of said foamed or fibrous gas-permeable layer and easily move within said layer through the walls of the container, passing through the porous drainage layer.
More particularly when a foam layer, such as a polystyrene foam layer, is employed as the substrate structural layer, even if an outer layer and a lid with a very low OTR are employed, the atmosphere within the package re-equilibrates with the outer atmosphere in just few hours. In such a case it is almost immaterial whether the heat-sealing of the lid to the tray rim is carried out by using conventional pressure conditions or a much higher pressure, as in any case the foamed cells with not be compressed to such an extent to exclude air permeation at the sealing area.
Also when a rigid layer is employed as the substrate structural layer but the absorbing layer is obtained, as indicated in EP-A-520,509, by a formulation of expanded and/or fibrous material, then in most of the cases air may pass through the side edges of such a highly gas permeable absorbing layer entering into the end package.
WO 00/46125 describes a self-absorbing food-packaging tray that comprises a “space” sealed in a fluid-tight manner and filled by a material from which the wall structure is made. The sealed space is obtained by bringing together the outer surface and the inner surface of the base wall. According to WO 00/46125 this can be obtained either by solvent or paint coating the distal edges of the tray rim to bridge the inner and the outer surfaces across the thickness of the wall structure at said peripheral edge (and in this case the sealed space and the tray would be conterminous) or by bringing together the inner and the lower surfaces by an ultrasonic seal or by the application of heat and pressure in a conventional thermoforming step. In certain instances, depending on the type of inner liners employed and/or of the way the tray is lidded, a gas-barrier package might be obtained.
No details are given in WO 00/46125 on how the ultrasonic sealing or the thermoforming steps must be performed to achieve sealing of the outer surface to the inner one with “disappearance” of the porous layer in-between at the sealing area. If sufficiently high pressures are exerted to fracture the intermediate porous layer and allow sealing of the inner surface to the outer one, the risk of cracking of the structure in the area closed to said seal and therefore the risk of leakers would probably be high.
Also difficult in the system of WO 00/46125 would be to guarantee consistent results in industrial conditions. Finally, with reference to what appears to be a preferred embodiment for the manufacture of a gas-barrier tray, where the structure comprises two gas-barrier liners, one on the outer surface and the other on the inner surface, recyclability of the skeleton would be impaired and the costs of the final product remarkably increased.
Thus, although WO 00/46125 describes a gas-barrier package using self-absorbing barrier foam tray, room for improvement exists in pursuit of a gas-barrier package based on a self-absorbing foam tray.
It is therefore an object of the present invention to provide a receptacle for food packaging which is capable of absorbing fluids exuded from the food product placed thereon without requiring the use of a separate pad and that at the same time may guarantee that the end package obtained by sealing to the receptacle flange a gas-barrier film will have gas-barrier properties.